Lessons Learned for Automating iOS Apps – What To Do When Tests Require Camera Roll Resources? February 18, 2015

Here at Animoto, the mobile application development team had spent some time over the past year investigating and implementing CI methodologies into the development cycle of the Animoto Video Maker application for iOS. A major part of this initiative involved creating automated test cases that would run at various times and circumstances.

First a bit of background. When we started this, we had already implemented a good amount of automation for the Animoto website. We had chosen to use Selenium and ran our automated tests against various browsers using Sauce Labs. It was decided to extend the existing infrastructure to support running automated tests using the Appium library against Sauce Labs. For those unfamiliar with mobile testing on Sauce Labs, they use the iOS and Android Simulators to run tests. I know, not ideal, but we can get to that another time.

The Problem

For anyone who has ever launched a fresh iOS Simulator (before Xcode 6), the OS is in it’s factory state. The Animoto Video Maker App transforms your pictures, video, and text, into professional looking videos… see where I’m going?

A lot of user flows depend on having some photos in the camera roll. A factory-fresh simulator without any photos means there are many flows we can’t automate. Unfortunately, at the time of writing, Sauce Labs does not have a way to upload assets to populate the Camera Roll, and the simulators are reset after executing each test case. Starting with XCode 6, the Camera Roll does have some images out of the box, but what was really needed were meaningful pictures and videos. So what is needed is a way to populate the Camera Roll while working within the constraints of running tests in Sauce Labs. Well, the app already reads images and pictures from Camera Roll, what about writing to it as well?

Adding or Altering Configuration Profile

Before we get to actually populating the Camera Roll, we need a mechanism to ensure that this logic is performed only when the intent is to run automation. Out of the box, Xcode provides 3 build configurations (Debug, Release, and Distribution). We can edit these configurations, add new ones, or even delete unnecessary ones. In this case, we can simply add a Test configuration to the mix. Once we did that, we were able to change various build settings to help create hooks for app automation. We can start out by adding a Preprocessor Macro for the Test build configuration, so that we can tell the pre-processor when to compile test hooks into the build.

Okay, now we can do some fun stuff with the build. For the sake of brevity, let’s focus specifically on the original issue: Getting pictures and videos into the Camera Roll.

Change Test Configuration Profile Settings

First things first – how does one get pictures and videos up to Sauce Labs? We can simply add them to the iOS project, but that would increase the size of the application bundle regardless of which build configuration is being used. Definitely not ideal. A better choice would be to store them somewhere externally and copy them to the application bundle when the Test configuration is used. This can be done by running a script when building the project.

Populating the Camera Roll

Now we have an application bundle that contains a bunch of sample pictures and videos. This is great because when the application gets uploaded to Sauce Labs for testing, so do all the sample data. The following code example assumes all the sample images are in a folder within the application bundle named ‘TestImages’:

The above code makes a bunch of assumptions. First, it only works for images. Another folder consisting of sample videos can be created, and the using similar logic and the writeVideoAtPathToSavedPhotosAlbum method. Next, calling writeImageToSavedPhotosAlbum can indeed fail. For the sake of keeping this example code more readable, error handling was excluded. Retry logic should be included if an error is returned.

Finally, you may have noticed the use of a semaphore in the example code. Writing images to the Camera Roll is actually an asynchronous call, meaning that the call returns immediately while a separate thread processes writing the image data to the Camera Roll. The writeImageToSavedPhotosAlbum method can fail if there are too many threads trying to write image data simultaneously. The semaphore is used ensure that images are written to the Camera Roll sequentially. This makes using the writeImageToSavedPhotosAlbum method much more stable.

Okay, so now that is left is to call the method when running the Test configuration. This can easily be done using the Preprocessor Macro setting that was above mentioned.

#if TEST
[ANTestClass populateCameraRoll];
#endif

It is recommended to call the method somewhere deterministic (ie -a button tap). Simply populating the Camera Roll at start-up may mess up launching Apples Instrumentation library because of the Alert displayed when the app accesses the Camera Roll for the first time. This lesson was learned the hard way.

This opens up the ability to add more automated test hooks into the application under test, but as a word of warning; the more hooks added, the more the test configuration of the app diverges from what is being released to customers.